Method for manufacturing automobile weather strip

ABSTRACT

An automobile trim has a trim body (a base layer) formed of a rubber composition and having a design surface, a decorating layer formed of a thermoplastic elastomer composition and thermally bonded integrally with the design surface of the trim body. A thermal bonding layer is formed of a thermoplastic resin composition and interposed between the decorating layer and the trim body so that the decorating layer is thermally bonded integrally with the trim body through the thermal bonding layer. The thermal bonding layer has a thickness to an extent not to prevent bending flexibility when the trim is attached to a vehicle body. In another example, a cushion layer is laminated on the trim body and formed of sponge rubber of EPDM, a decorating layer is laminated on the cushion layer and formed by foaming olefin thermoplastic elastomer, and an olefin bonding layer for bonding the cushion layer and the decorating layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automobile trim in which adecorating layer is formed of a TPE (thermoplastic elastomer)composition and integrated with a design surface of a trim body which isformed of a rubber composition.

Here, a weather strip (automobile trim) having a trim portion and a sealportion will be mainly described as a product to which the presentinvention is applied, by way of example. The present invention isapplicable also to a weather strip of another type, such as a glass runhaving a trim portion, or the like. Further, the present invention isapplicable also to an automobile trim having only a trim portion withouthaving any seal portion.

The present application is based on Japanese Patent Applications Nos.2000-60000 and 2000-278062, which are incorporated herein by reference.

2. Description of the Related Art

A trim portion and a seal portion of a weather strip are usuallymanufactured using EPDM (ethylene-propylene-diene copolymer)compositions of a solid recipe and a foam recipe, respectively, bytwo-layer extrusion (co-extrusion) by using a two-layer extruder. Thereason why such EPDM compositions are used is that they are superior inweatherability and elasticity and low in specific gravity so that theycan contribute also to making the weather strip light in weight. Asulfuric vulcanizer which is a general-purpose vulcanizer is usuallyused for vulcanizing the EPDM compositions. That is because hot-airvulcanization used for continuous vulcanizing extruded products isapplicable to the sulfuric vulcanizer differently from othergeneral-purpose vulcanizers of peroxides.

Then, for forming the decorating layer in the trim portion, there aremethods in which a decorating layer composed of TPE (composition), whichhas not solidified yet, is laminated and integrated on the surface of atrim body (base layer) by thermal bonding without using any bondingagent (U.S. Pat. No. 4,537,825, European Patent No. 0372745, andUnexamined Japanese Patent Publication No. Hei. 8-230013). These methodsare more superior in productivity to conventional methods in which asoft thermoplastic resin sheet is cut out and bonded by a bonding agentso as to form a decorating layer. Here, the reason why the decoratinglayer is formed of TPE is to ensure the easiness of bending when thetrim portion of the weather strip is attached to a vehicle body flangeor the like.

However, in the weather strip configured so that the decorating layerformed by the above-mentioned method has been thermally bondedintegrally with the surface of the trim body, it has been found that thefollowing problems occur in the decorating layer.

(1) The decorating layer is affected by the ground color of the trimbody (base layer) so that the decorating layer is difficult to exhibit arequired color. This is because a large quantity of carbon black as arubber reinforcement is mixed into the solid-recipe EPDM composition forforming the trim body so that the solid-recipe EPDM composition has ahigh degree of blackness (chroma saturation).

(2) The decorating layer is affected by sunlight chronologically so thatthe decorating layer is apt to yellow. As the cause thereof, it has beenconfirmed that there is a high possibility that such yellowing is causedby the migration of a sulfuric vulcanizing agent (sulfur and vulcanizingaccelerator thereof) in vulcanized rubber to the decorating layer (seeUnexamined Japanese Patent Publication No. Hei. 9-193299).

The influence of the ground color and the yellowing degree in thedecorating layer becomes more conspicuous if the coloring of thedecorating layer is bright or pale. That is, in the above-mentionedweather strip (trim) configured so that the decorating layer has beenthermally bonded with the trim body, it is difficult to meet a requestof making the decorating layer bright or pale.

To prevent the decorating layer from yellowing easily, it has beenproposed in the above-mentioned patent publication (Unexamined JapanesePaten No. Hei. 9-193299) that hydrotalcite as an anti-discoloring agentis mixed into the TPE composition for forming the decorating layer.

However, hydrotalcite is currently so expensive as to increase the totalmaterial cost of the weather strip. Therefore, other measures againstthe yellowing of the decorating layer without using hydrotalcite aredesired.

Further, a technique disclosed in Unexamined Japanese Patent PublicationNo. Hei. 6-16094 has also been known as such another automobile weatherstrip. This weather strip has a rubber base, a decorating skin material,and a cushion layer. The rubber base is composed of solid rubber of EPDM(aforementioned solid recipe) which is a kind of EPR (ethylene-propylenerubber) . The decorating skin material (aforementioned decorating layer)covers a portion of the rubber base in the area where the rubber base(layer) is exposed in the cabin of a vehicle. The cushion layer isformed of sponge rubber of EPDM (aforementioned foam recipe) between thedecorating skin material and the base (layer). The cushion layer sinksfollowing external force through the decorating skin material, andrestores its original shape in response to the release of the externalforce. Thus, the cushion layer provides a soft feeling on the sense oftouch.

However, the decorating skin material attached to the surface of thecushion layer is of cloth using precolored polyester fibers as rawmaterial, or of a resin sheet material such as PVC. Therefore, a softfeeling on the external appearance cannot be obtained from the skinmaterial itself. In addition, in either case of polyester or PVC, theyhave no adhesive property to the rubber base of EPDM. Accordingly, it isnecessary to prepare a special bonding film having a two-layer structurewith adhesive properties to bond to the skin material and the EPDMrubber base respectively. As a result, the manufacturing cost isincreased. Further, in this weather strip, the cushion layer is providedonly between the apex portion of the sectionally U-shaped rubber baseand the skin material. An outside lip projecting on the car-interiorside is formed of solid rubber alone. Therefore, a soft feeling cannotbe obtained in this portion sufficiently. Thus, there has been a problemthat a soft feeling and a sense of high quality cannot be obtainedsufficiently as a car interior material.

SUMMARY OF THE INVENTION

In consideration of the aforementioned problems, it is an object of thepresent invention to provide an automobile trim which can reduce theinfluence of the ground color (black) of a trim body on a decoratinglayer, and which can further reduce the influence of a discoloring agentmigrating from the trim body to the decorating layer.

It is another object of the present invention to provide an automobileweather strip which can provide a soft feeling not only on the sense oftouch but also on the external appearance in the portion where a skinlayer as a decorating layer is provided, and all over the surface, andwhich can be manufactured at a comparatively low price, and a method formanufacturing such a weather strip.

The present inventors made diligent efforts toward development in orderto solve the foregoing problems. As a result, the present inventorsfound that when a decorating layer was thermally bonded with a trim bodythrough a thermal bonding layer having a predetermined thickness, theinfluence of the ground color and the yellowing degree as describedabove could be reduced practically even if the thermal bonding layer wasthin enough not to block the bending flexibility when the trim wasattached to a vehicle body. Thus, the present inventors came to thinkout an automobile trim having the following configuration.

The automobile trim according to the present invention comprises: a trimbody formed of a rubber composition and having a design surface; and adecorating layer formed of a thermoplastic elastomer composition (TPEcomposition) and thermally bonded integrally with the design surface ofthe trim body; wherein the decorating layer is thermally bondedintegrally with the trim body through a thermal bonding layer formed ofa thermoplastic resin composition between the decorating layer and thetrim body, the thermal bonding layer having a thickness to an extent notto prevent bending flexibility when the trim is attached to a vehiclebody.

With such a configuration, it is preferable that the thermal bondinglayer has a thickness with which the ground color of the trim body canbe hidden and further with which a discoloring agent including asulfuric agent can be prevented from migrating from the trim body to thedecorating layer.

In addition, it is preferable that base polymers of the TPE composition,the rubber composition and the thermoplastic resin composition areolefin TPE (TPO), ethylene-α-olefin-nonconjugate-diene copolymer rubber(EPDM), and olefin resin, respectively. Particularly, it is preferablethat the base polymer of the thermoplastic resin composition is linearlow-density polyethylene. The thickness of the thermal bonding layer inthis configuration is usually in a range of from 40 μm to 300 μm,preferably in a range of from 80 μm to 150 μm.

Further, if the TPE decorating layer is of foam, the decorating layercan be thermally bonded integrally with the trim body without collapsingcells of the foam.

Further, there is provided an automobile weather strip comprising: anattachment base portion attached to a vehicle-body-side member andcomposed of solid rubber of EPR; a cushion layer laminated on theattachment base portion and formed of sponge rubber of EPR; a skin layerlaminated on the cushion layer and formed by foaming olefinthermoplastic elastomer; and an olefin bonding layer for bonding thecushion layer and the skin layer.

The above automobile weather strip is attached to the vehicle-body-sidemember on the attachment base portion composed of solid rubber of EPR.The skin layer is attached onto the attachment base portion through thecushion layer and the bonding layer. The skin layer is a foamed layer sothat it can provide a soft feeling on the external appearance. Inaddition, the cushion layer disposed under the skin layer is formed ofsponge rubber of EPR, and provided substantially all over the portionwhere the skin layer is provided. Thus, the cushion layer can provide asoft feeling on the sense of touch. In addition, all of the attachmentbase portion, the cushion layer and the skin layer are formed ofmaterials of olefin series so that they are thermally bonded with oneanother firmly. Thus, there is no fear that they peel off.

Still further, there is provided a method for manufacturing anautomobile weather strip, comprising the steps of: extruding EPR to forman extrusion body as the attachment base portion and the cushion layer;vulcanizing the extrusion body; extruding foamable olefin thermoplasticelastomer to form the skin layer while extruding a skin sheet so that abonding sheet composed of an olefin material for forming the bondinglayer is interposed between the skin sheet and the cushion layer; andlaminating the skin sheet, the bonding sheet and the extrusion body,respectively at the predetermined temperature, so as to keep cells offoam of the skin sheet, while laminating the skin sheet, the bondingsheet and the extrusion body and pressing the laminated three by rollersso as to thermal bond the skin sheet onto the cushion layer through thebonding sheet.

Features and advantages of the invention will be evident from thefollowing detailed description of the preferred embodiments described inconjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 shows a sectional view of an embodiment of a weather stripaccording to the present invention;

FIG. 2 shows a sectional view of another embodiment of a weather stripaccording to the present invention;

FIG. 3 shows a schematic view showing whole steps of the method formanufacturing the weather strip in FIG. 1;

FIG. 4 shows a front view showing the positional relationship between alaminated film extrusion die and a vulcanized rubber extruded body inFIG. 3;

FIG. 5 shows an external appearance view showing an automobile body towhich a weather strip has been attached;

FIG. 6 shows a sectional view showing a still another embodiment of aweather strip according to the present invention;

FIG. 7 shows an explanatory enlarged view showing a laminated structureof a cushion layer and a skin layer;

FIG. 8 shows a schematic view showing a production line for the weatherstrip; and

FIG. 9 shows a sectional view showing a still another embodiment of aweather strip according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The aforementioned configurations of the present invention will bedescribed below in detail, respectively. Incidentally, any compoundingunit is a weight unit without notice.

FIG. 5 shows an external appearance view showing an automobile body BDto which a weather strip according to the present invention 12 or 12Ahas been attached.

A weather strip 12 (12A) has a trim portion 14 (14A) and a hollow sealportion 16 (16A) as shown in FIGS. 1 and 2.

Here, the trim portion 14 (14A) has a basically U-shape in section whichwill be a flange holding portion in the illustrated embodiment. However,the present invention is applicable to a trim portion having anothershape.

The trim portion 14 (14A) has two pairs of holding lip portions 26 and26 in FIG. 1. On the other hand, in FIG. 2, the trim portion 14 (14A)has one pressing lip portion 28 on one side and three support lipportions 30 on the other side. Then, in FIG. 2, a covering lip 36 forcovering a gap between an inner garnish 32 and a vehicle body flange 34(34A) is provided to extend from the apex portion of the U-shape of thetrim portion 14A. Incidentally, an insert metal-core 19 is embedded inthe trim portion 14 (14A). An opening trim weather strip attached to thecircumferential edge of a door opening portion in FIG. 1 will bedescribed below by way of example. Parts similar to those in FIG. 2 arereferenced correspondingly with the suffix “A”, and description thereofwill be omitted.

In the trim portion (trim) 14, a solid decorating layer 18 formed of athermoplastic elastomer (TPE) composition is thermally bonded integrallywith a design surface of a trim body (hereinafter referred to as “baselayer”) 20. The insert metal core 19 is embedded in the inside of thebase layer 20, which is formed of a rubber composition. Then, a thermalbonding layer 22 formed of a thermoplastic resin composition isinterposed between the decorating layer 18 and the base layer 20. Thus,the decorating layer 18 is thermally bonded integrally with the baselayer 20 through the thermal bonding layer 22.

The rubber composition for forming the base layer 20 is usually made ofa solid rubber recipe from the point of view of ensuring the shaperetentivity of the trim portion 14. The rubber composition may be madeof a fine foam recipe (the expansion ratio is not higher than 1.5) fromthe point of view of making the trim portion 14 light in weight. Thehollow seal portion 16 is made of a sponge rubber (foamed rubber) recipefrom the point of view of ensuring the elasticity and the sealingperformance.

Examples of rubber polymers (base polymers) for the rubber compositioninclude ethylene-α-olefin-nonconjugate-diene copolymer rubber (EPDM),styrene-butadiene copolymer rubber (SBR), chloroprene rubber (CR), etc.Particularly, EPDM is preferable from the point of view of durability,age resistance such as light resistance, ozone resistance, weatherresistance, or the like, and making the trim portion 14 light in weight.

Examples of α-olefin in the EPDM include propylene, 1-butene, 1-pentene,1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, etc. Of them,propylene is preferable. On the other hand, examples of nonconjugatediene include 1,4-hexadiene, dicyclopentadiene,5-ethylidene-2-norbornene, etc.

Examples of preferable ethylene-α-olefin copolymer rubber includeethylene-propylen copolymer rubber, ethylene-propylene-ethylidenenorbornene copolymer rubber, ethylene-propylene-dicyclopentadienecopolymer rubber, etc.

As a vulcanizer for the EPDM composition, a sulfuric vulcanizer which isa general-purpose vulcanizer is usually used as mentioned above.

Here, a sulfuric vulcanizing agent and a vulcanizing accelerator thereofare included in such a sulfuric vulcanizer. Examples of such sulfuricvulcanizing agents include active sulfur releasing organic vulcanizingagents as well as sulfur. Examples of the active sulfur releasingorganic vulcanizing agents include morpholine disulfide, alkyl phenoldisulfide, organic polysulfide copolymer, and further sulfur containingvulcanizing accelerators such as thiuram one, thiourea one, or the like.Further, in the present invention, a peroxide vulcanizing agent, apolyamine vulcanizing agent, etc. can be used together suitably inaccordance with necessity.

In addition to the above-mentioned sulfuric vulcanizer, carbon black,process oil, lubricant, inorganic filler, age resistor, and othersub-materials are suitably mixed into the rubber composition so as toform an extrusion-molding rubber material for the base layer 20 bykneading or the like.

Incidentally, the vulcanizer for the rubber composition is not limitedto the sulfuric vulcanizer, but it may be another vulcanizer such as aperoxide vulcanizer or the like.

As the base polymer of the TPE composition for forming the decoratinglayer 18 according to the present invention, if the base layer (trimbody) 20 is formed of a non-polar rubber composition such as EPDM,non-polar TPE such as olefin TPE (TPO), styrene TPE (TPS), or the like,is used in the same manner as that in conventional one. Thus, thethermal bond properties of both the base layer 20 and the decoratinglayer 18 with the thermal bonding layer are ensured easily.

On the contrary, if the base layer is formed of polar rubber such aschloroprene rubber (CR), polar TPE such as vinyl chloride TPE, polyesterTPE, polyamide TPE, or the like, is used.

Because the base layer is usually formed of EPDM, detailed descriptionwill be made about A. TPO and B. TPS which are preferable TPEs to becombined with EPDM.

A. TPO is typically made of olefin resin and ethylene-α-olefin copolymerrubber (EPR). The weight ratio of the former to the latter is in a rangeof from 10/90 to 90/10, preferably in a range of from 30/70 to 80/20.

Particularly, polypropylene is preferable as the olefin resin from thepoint of view of reducing the weight. Examples of α-olefin the carbonnumber of which is 2 or more include ethylene, 1-butene, 1-pentene,3-methyl-1-butene, 1-hexene, 1-decene, 3-methyl-1-pentene,4-methyl-1-pentene, 1-octene, etc. The olefin resin used has a melt flowrate (MFR; 2.16 kg load) usually in a range of from 0.1 g/10 min to 100g/10 min, preferably in a range of from 0.5 g/10 min to 50 g/10 min.

As the ethylene-α-olefin copolymer rubber (EPR), ethylene-α-olefincopolymer rubber (EPM), ethylene-α-olefin-nonconjugate-diene copolymerrubber (EPDM), or the like, can be used. Here, as the α-olefin, the sameas that in EPDM of the base layer can be used. Usually, propylene isused.

The weight ratio of ethylene to α-olefin is usually in a range of from90/10 to 30/70, preferably in a range of from 85/15 to 45/55. Whenethylene-α-olefin-nonconjugate-diene copolymer rubber is used, thecontent of nonconjugate diene is usually in a range of from 5 to 40 byiodine value. Incidentally, ethylene-α-olefin copolymer rubber andethylene-α-olefin-nonconjugate-diene copolymer rubber may be used andmixed together. Further, oil extended rubber may be used.

The Mooney viscosity (ML₁₊₄ 100° C.) of the above-mentioned EPR isusually in a range of from 10 to 350, preferably in a range of from 30to 300. If the Mooney viscosity is too low, the EPR may be inferior inmechanical strength such as abrasion resistance. On the contrary, if theMooney viscosity is too high, irregularities are apt to be produced inthe surface of the decorating layer 18. Thus, the external appearancemay be marred.

In the TPE composition, the EPR is kept in an unbridged state or putinto abridged state such as a partial bridged state, a dynamic bridgedstate, or the like, suitably. When the EPR is bridged, the solventresistance and the mechanical strength of the TPO can be improved.

B. TPS is made of olefin resin andaromatic-vinyl-conjugate-diene-compound block copolymer or hydrogenatedone thereof. The weight ratio of the former to the latter is in a rangeof from 10/90 to 90/10, preferably in a range of from 30/70 to 80/20.

As the olefin resin, the same as that in the above-mentioned TPO can beused.

Examples of the aromatic-vinyl compound in the copolymer includestyrene, α-methylstyrene, p-methylstyrene, vinyl toluene, etc. Of them,styrene is preferable. Examples of the conjugate diene compound includebutadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc. Ofthem, butadiene and isoprene are preferable.

The structure of the copolymer is of a linear block copolymer expressedby the general formula (A—B)_(n), A—(B—A)_(n) or B—(A—B)_(n) (where Adesignates a copolymer block mainly composed of aromatic vinyl compound,and B designates a copolymer block mainly composed of conjugate dienecompound, but the border between the blocks A and B is not alwaysnecessary to be distinguished clearly; and where n is an integer of 1 ormore) or a branched (radial) block copolymer expressed by the generalformula [(A—B)_(n)]_(m)—X, [A—(B—A)_(n)]_(m)—X or [B—(A—B)_(n)]_(m)—X(where A and B designates copolymer blocks in the same manner asmentioned above, and X designates a brancher residue; and where n is aninteger of 1 or more, and m is an integer of 3 or more).

The number-average molecular weight (M_(n)) of the copolymer is usuallyin a range of from 5,000 to 500,000, preferably in a range of from10,000 to 300,000. If the number-average molecular weight is not largerthan 5,000, the mechanical strength of TPE becomes low. On the contrary,if the number-average molecular weight is not smaller than 500,000, theviscosity of a polymerization solution becomes high. Thus,polymerization needs to be performed at a low concentration so that theproductivity is lowered. It is preferable that the content of aromaticvinyl compound in the copolymer is in a range of from 10 wt % to 50 wt%.

Although the copolymer is used as it is, the copolymer is preferablyhydrogenated (reduced in double bond) from the point of view of lightresistance, weather resistance, thermal stability, or the like. Inaddition, EPR may be used together.

The copolymer or the hydrogenated copolymer is used as it is keptunbridged or put into a bridged state such as a full bridged state, apartial bridged state, or the like. If the copolymer is bridged, thesolvent resistance or the like of TPS is improved in the same manner asthat in the above-mentioned case of TPO. In addition, the mechanicalstrength is also increased.

A coloring agent (pigment, dye stuff) for decorating is essentiallymixed into the above-mentioned TPE composition. Additives such as aninorganic filler such as talc, calcium carbonate, or the like, a fireretardant, a lubricant, an antistat, an age resistor(heat-resistance/light-resistance stabilizer), etc. are suitably addedto the TPE composition. After being extruded and kneaded, the TPEcomposition is granulated (pelletized) to form an extrusion-moldingmaterial.

A peroxide unbridged hydrocarbon rubber-like substance represented bypolyisobutene, butyle rubber, or the like, and/or a mineral oil softenermay be mixed into the TPE composition in accordance with necessity.Then, the loading of the mineral oil softener is usually set to be in arange of from 5 phr to 200 phr.

As the base polymer of the thermoplastic resin composition for formingthe thermal bonding layer 22, non-polar thermoplastic resin such asolefin resin, styrene resin, or the like, when the base polymers of thebase layer 20 and the decorating layer 18 are non-polar. On thecontrary, when the base polymers of the base layer 20 and the decoratinglayer 18 are polar, polar thermoplastic rein such as vinyl chlorideresin, polyester resin, polyamide resin, or the like, is used. Suchresins are used for ensuring the heat seal property respectively.

As such olefin resin, copolymers of polyethylene (PE), polypropylene(PP) or propylene with α-olefin the carbon number of which is two ormore, or the like, may be used. Of them, low-density polyethylene (LDPE)is especially preferable because it has a low melting point and it isrich in flexibility. Particularly, linear low-density polyethylene(LLDPE) is preferable because it is superior in heat resistance andmechanical strength. Incidentally, the melt temperatures ofhigh-pressure-processed polyethylene (low-density polyethylene),medium-pressure-processed polyethylene (medium-density polyethylene),and low-pressure-processed polyethylene (high-density polyethylene) are98° C., 120° C. and 124° C., respectively. (See p.713 of “Handbook ofPlastics-Processing Technique, New Edition”, edited by“Plastic-Processing Technique Handbook Editorial Committee”, publishedby THE NIKKAN KOGYO SHIMBUN, LTD., Dec. 20, 1977).

The thermoplastic resin composition may be composed of thermoplasticresin alone. However, in order to ensure flowability and tackiness atthe time of melting, a softener (plasticizer, process oil, lubricant,etc.), a tackifier, and further an additive such as an age resistor, orthe like, are added and mixed suitably. Then, in the same manner as inthe case of the TPE composition, those agents are added to thermoplasticresin, extruded and kneaded, and thereafter granulated (pelletized) soas to form an extrusion-molding material.

Then, the thermal bonding layer 22 in the present invention is set tohave a thickness with which the bending flexibility of the weather strip(trim) is not blocked when it is attached to the vehicle body. Thethickness of the thermal bonding layer 22 is determined by the balancewith the ability to hide the ground color of the base layer 20, andfurther the ability to block the migration of a discoloring agentincluding a sulfuric agent from the base layer 20 to the decoratinglayer 18.

For example, in the case of the combination of the base layer 20 ofEPDM, the thermal bonding layer 22 of LDPE, and the decorating layer 18of TPO, the thickness of the thermal bonding layer 22 is set to be in arange of from 40 μm to 300 μm, preferably in a range of from 80 μm to150 μm. If the thermal bonding layer 22 is too thin, it becomesdifficult to ensure the ground color hiding ability and the discoloringagent migration blocking ability described above. On the contrary, ifthe thermal bonding layer 22 is too thick, it becomes difficult toensure the bending flexibility of the weather strip when it is attachedto the vehicle body.

Incidentally, the thickness of the decorating layer 18 is set to beusually in a range of from 200 μm to 1,000 μm, preferably in a range offrom 300 μm to 800 μm. If the decorating layer 18 is too thin, itbecomes difficult to obtain an impressive clear color. On the contrary,if the decorating layer 18 is too thick, the loading of a decoratinglayer material which is more expensive than a base layer materialincreases.

Next, a method for manufacturing the above-mentioned weather strip willbe described about the case where the weather strip as shown in FIG. 1is manufactured.

If the method proposed in the above-mentioned Unexamined Japanese PatentPublication No. Hei. 8-230013 is applied to the following manufacturingmethod, it is easy to control the thickness (see FIGS. 3 and 4).Accordingly, the following method is preferable though otherconventional methods can be adopted.

I. First, a cross-head type two-layer extruder 42 for a weather stripbody 13 is used to extrude the weather strip body 13 with the base layer20 and the hollow seal portion 16. Then, the weather strip body 13 isvulcanized by a microwave heater (UHF) 44 and a hot-air vulcanizer (HAV)46. Thus, the weather strip body 13 is obtained as a vulcanized rubberextruded body.

II. Next, a TPE composition and thermoplastic resin are laminated andextruded (two-layer extruded), respectively, with a predeterminedthickness and width by a two-layer extruder 48 for a laminated film, soas to form a laminated film 23 composed of the decorating layer 18 andthe thermal bonding layer 22. Then, before being solidified, thelaminated film 23 is pressed onto the upper surface of the weather stripbody 13 by pressure rollers 52 and 54. Thus, the laminated film 23 isthermally bonded with the weather strip body (base layer) 13 (see FIG.3). Incidentally, the laminated film 23 is extruded into a predeterminedshape in the form in which the thermal bonding layer 22 has beenthermally bonded with the lower surface of the decorating layer 18.

That is, the two-layer extruder 48 for a film is disposed in a positionwhere the vulcanizing step (in the illustrated example, outside the exitside of the hot-air vulcanizer 46) of the weather strip body 13 isfinished. Further, the first and second pressure rollers 52 and 54 forpressing the laminated film 23 onto the upper surface and the endsurface of the weather strip body 13 respectively are sequentiallyconnected to the vicinity of the exit side of a film extrusion die 50 ofthe extruder 48. Then, in the illustrated embodiment, the referencenumerals 58 represent take-up rollers. In addition, a support roller 56may be disposed correspondingly to the first pressure roller 52 (see thetwo-dot chain line in FIG. 3).

The thickness of the thermal bonding layer 22 is set to be in a range offrom 50 μm to 150 μm, preferably in a range of from 80 μm to 120 μm. Onthe other hand, the thickness of the decorating layer 18 is set to be ina range of from 400 μm to 600 μm, preferably in a range of from 450 μmto 550 μm.

Here, in the condition that the thermal bonding layer 22 has been set atthe melt temperature (100° C. to 130° C. in the case of low-density PE)of the thermoplastic resin (thermal bonding layer 22), the thermalbonding layer 22 is supplied as the laminated film 23 between the firstand second pressure rollers 52 and 54 and the base layer 20 (vulcanizedrubber extruded body). Thus, a reliable heat seal property is ensuredbetween the base layer 20 and the decorating layer 18. Further, thelaminated film 23 is cooled below the melt temperature of thethermoplastic resin in the first and second pressure rollers 52 and 54,and fed forward from the first and second pressure rollers 52 and 54.Thus, the thermal bonding layer 22 is solidified while the decoratinglayer 18 and the base layer 20 are thermally bonded and integrallyconnected with each other.

The controlled temperatures of the first and second pressure rollers areusually set to be in a range of from 40° C. to 50° C. The thermoplasticresin is extruded at a higher temperature than the melt temperaturethereof so as to form the laminated film 23 together with the decoratinglayer 18. Then, the thermal bonding layer 22 is pressed and bonded ontothe base layer 20 in the condition that the thermal bonding layer 22 canbe thermally bonded. Incidentally, it is preferable that the temperatureof the weather strip body 13 (base layer 20) is also kept in a range offrom 60° C. to 120° C. This is because the thermal bonding layer 22composed of a thermoplastic resin composition is to be supplied surelybetween the first and second pressure rollers 52 and 54 and thevulcanized rubber extruded body at a temperature beyond the melttemperature thereof.

As the decorating layer 18, foamed elastomer may be used. Particularly,fine foamed elastomer the expansion ratio of which is in a range of nothigher than 1.5, preferably in a range of from 1.05 to 1.45, may beused. In this case, the surface of the decorating layer 18 may be madeleathery. Alternately, the surface of the foam may be buffed to fluffthe surface of the decorating layer 18. Further, the first pressureroller 52 may be provided as an embossing roller so that the decoratinglayer 18 is subjected to embossing processing.

Incidentally, when the decorating layer 18 is composed of foamedelastomer, cells of the foam may be collapsed by the pressure by thepressure rollers in a conventional structure where there is no thermalbonding layer. However, the bonding force is improved by theinterposition of the thermal bonding layer so that the pressing force ofthe pressure rollers can be reduced in comparison with the conventionalstructure in which there is provided no thermal bonding layer. Thus,there is no fear that the cells of the foam are collapsed.

In the above description, the decorating layer 18 provided with themelted thermal bonding layer 22 was pressed onto the base layer(vulcanized rubber body) 20 so as to form a decorating layer. However,the base layer 20, the decorating layer 18 and the thermal bonding layer22 may be extruded from one extrusion die simultaneously so as to bethermally bonded integrally with each other. Alternatively, a laminatedfilm (a decorating layer provided with a thermal bonding layer) may bepressed and thermally bonded onto the unvulcanized rubber base layer 20immediately after extrusion. Further, while the laminated film 23 formedlike a tape in another position in advance is supplied from a reel, oneor both of the thermal bonding layer 22 and the base layer 20 may beheated to a temperature with which the thermal bonding layer 22 can bethermally bonded. Thus, the laminated film 23 is integrated with thebase layer 20.

The weather strip manufactured thus is processed so that the trimportion is bent into a U-shape as shown in FIG. 1, and suitablyconnected like a ring. Then, for use, the weather strip is attached tothe vehicle body flange 34 of the vehicle. The weather strip shown inFIG. 2 is manufactured and attached in the same manner. Incidentally,the reference numerals 38 and 38A represent door panels in FIGS. 1 and 2respectively.

The automobile trim according to the present invention, which isconfigured thus, has the following operations and effects.

Although the thermal bonding layer is formed of thermoplastic resinwhich is not flexible compared with TPE, the thermal bonding layer isthin enough not to block the bending flexibility of the automobile trim(weather strip) or the like when it is attached to a vehicle body.Accordingly, the workability of attaching the automobile trim to thevehicle body is the same as that in conventional one.

In addition, due to the presence of the thermal bonding layer, theinfluence of the ground color of the base layer on the decorating layeris reduced and the migration of a discoloring agent contained in thebase layer to the decorating layer is also reduced. Accordingly, a clearbright color or a clear pale color is obtained easily in the decoratinglayer on the surface of the trim body. In addition, chronologicaldiscoloration (yellowing or the like) of the decorating layer caused bythe discoloring agent is lowered.

Further, when the base layer is formed of a rubber composition of a finefoam recipe, the thermal bonding layer does not contain an inorganicfiller substantially, and it is richer in flowability than TPE.Accordingly, the thermal bonding layer also enters surface pores of thebase layer so that the welding strength (bonding strength) increases.

Further, when the decorating layer is formed of a TPE composition of afoam recipe, the surface can be made leathery. In addition, because thethermal bonding layer is provided, the bonding force can be improved.Accordingly, the pressure force of pressure rollers can be reduced incomparison with that in a conventional case where no thermal bondinglayer is provided. Thus, there is no fear that cells of the foam arecollapsed.

Next, description concerning the specific Example and Comparative areprovided.

In a weather strip having a sectional shape shown in FIG. 1, a trimportion was extruded and vulcanized using the following EPDMcomposition. Then, in the condition that the surface temperature of thetrim portion was 90±5° C., a laminated film composed of a decoratinglayer (500 μm) and a thermal bonding layer (100 μm) was two-layerextruded (extrusion heat temperature: 200° C.) using the following TPOcomposition and LLDPE. The laminated film was thermally bonded bypressure rollers so that a weather strip of Example was prepared. Thetemperature of the thermal bonding layer at that time was set to be120±5° C.

In addition, on similar conditions, instead of the laminated film, asingle-layer film composed of only a decorating layer was thermallybonded onto a base layer in the same manner. Thus, a weather strip ofComparative was prepared.

Of the weather strips prepared thus, the decorating layer in the weatherstrip in Example exhibited clear white, while the decorating layer inthe weather strip in Comparative was grayish.

In addition, a light resistance test (83° C.×300 h) was performed on therespective weather strips. The weather strip of Example did not yellowwhile the weather strip of Comparative yellowed.

EPDM Composition Recipe

EPDM 100 parts MAF carbon 100 parts plasticizer 60 parts zinc oxide 10parts stearic acid 3 parts sulfur 1.5 parts vulcanizing accelerator 5parts

TPO Composition

dynamic vulcanizing TPO 100 parts (PP/EPDM = 20/80) paraffinic processoil 5 parts white pigment (TiO₂ series) 1.2 parts

LLDPE Specification

melt temperature (JIS K 7121) 120° C. density (underwater displacement:JIS K 7112) 0.92

Another embodiment of the present invention will be describedhereinafter.

FIG. 5 is an external appearance view showing an automobile body BD towhich a weather strip 100 is attached. Specifically, the weather strip100 is attached to a circumferential edge portion of a door opening D ofthe automobile body BD. FIG. 6 is a sectional view showing the weatherstrip (weather strip door opening trim) 100.

In FIG. 6, the weather strip 100 has an attachment base portion 112 as abase layer, a cushion layer 118, a skin layer 120 as a decorating layer,an olefin bonding layer 122, a hollow seal portion 124, and an outsidelip 118 a. The attachment base portion 112 is attached to avehicle-body-side member, and composed of solid rubber of EPDM (solidrecipe) which is a kind of EPR. The cushion layer 118 is laminated onthe attachment base portion 112, and formed of sponge rubber of EPDM(foam recipe). The skin layer 120 is laminated on the cushion layer 118,and formed by foaming olefin thermoplastic elastomer. The bonding layer122 bonds the cushion layer 118 and the skin layer 120 with each other.The hollow seal portion 124 is provided to project from one side surface(car-exterior side) of the attachment base portion 112. The outside lip118 a is provided to project from the other side surface (car-interiorside) of the attachment base portion 112.

The attachment base portion 112 has a rubber base 113 composed ofsectionally U-shaped solid rubber, and support lips 114 projectingtoward the inside of the rubber base 113. An insert core 116 is embeddedin the rubber base 113 so as to retain the U-shape of the rubber base113.

The cushion layer 118 has an outside lip 118 a projecting to come intopressure contact with an interior member W inside the cabin of thevehicle. The cushion layer 118 is disposed substantially all over theregion from the tip end portion of the outside lip 118 a to the baseportion of the hollow seal portion 124, that is, the prospectivedecoration area of the rubber base 113 which is exposed in the cabin ofthe vehicle. The cushion layer 118 is formed of low-density foamedsponge rubber of EPDM at a thickness in a range of from 1 to 8 mm. Thecushion layer 118 is formed to sink following external force through theskin layer 120 and restore its original shape in response to the releaseof the external force. Incidentally, the rubber base 113 and the cushionlayer 118 are extruded integrally with each other by simultaneousextrusion molding, and vulcanized simultaneously to be bonded with eachother.

FIG. 7 is an explanatory enlarged view showing the lamination structureof the cushion layer 118 and the skin layer 120. The skin layer 120 isbonded with the cushion layer 118 through the bonding layer 122 for usefor thermal bonding. The skin layer 120 is formed into a sheet byfoaming olefin thermoplastic elastomer. The thickness of the skin layer120 is in a range of from 0.3 mm to 0.7 mm. Incidentally, coloringmatters, pigments, dye stuffs, or the like, are added to the skin layer120 so that the skin layer 120 is precolored in a color matched to thecolor tone of the cabin of the vehicle.

The bonding layer 122 is interposed in the form of a film-like layerbetween the skin layer 120 and the cushion layer 118 so as to heat-sealthem with each other. The bonding layer 122 is formed of polyethylene(PE) having a melting point in a range of from 110° C. to 140° C. Thebonding layer 122 is about 0.1 mm thick. The bonding layer 122 carriesout not only the operation of bonding but also the operation of blockinga residual sulfuric vulcanizing agent or the like bleeding on thesurface after the rubber base 113 and the cushion layer 118 have beenvulcanized. Thus, the bonding layer 122 prevents the sulfuricvulcanizing agent or the like from migrating to the skin layer 120. Inconsideration of such operations, the thickness of the bonding layer 122is established so as not to lose a soft feeling. In addition, when afilm of bright color such as white is used, the bonding layer 122 blocksthe black color of the rubber of the sponge rubber cushion layer 118.Thus, the bonding layer 122 carries out the operation of keeping thecoloring of the skin layer 120 bright.

The hollow seal portion 124 is formed of sponge rubber so as to projectin a hollow state from one side surface (car-exterior side) of therubber base 113. Thus, the hollow seal portion 124 carries out theoperation of sealing in cooperation with a door-side member.

Next, a method for manufacturing the foregoing weather strip 100 will bedescribed with reference to the schematic view of FIG. 8 showing aproduction line. As shown in FIG. 8, first, the rubber base 113 and soon are extrusion. A cross-head type extruder 130 is used forextrusion-molding. That is, the extruder 130 has a solid rubber extruder132, sponge rubber extruders 134 and 136, and an insert core feeder 140.The solid rubber extruder 132 has a cylinder and a screw. The cylinderof the extruder 132 is filled with an unvulcanized EPDM solid rubber rawmaterial. Similarly to the extruder 132, each of the sponge rubberextruders 134 and 136 has a cylinder and a screw. The cylinder of eachof the extruders 134 and 136 is filled with an unvulcanized EPDM spongerubber raw material. The insert core feeder 140 provides an insert coremember 116A which will be provided as the insert core 116. The extruder130 carries out so-called co-extrusion. That is, the solid rubber rawmaterial, the sponge rubber raw materials, and the insert core member116A are supplied simultaneously to one extrusion head and extrudedtherefrom simultaneously so as to form an extrusion body 112A.Sub-materials such as a reinforcement (carbon black), a plasticizer, alubricant, a vulcanizing agent, etc. are usually mixed to the EPDM solidrubber raw material and the sponge rubber raw materials. Incidentally, afoaming agent other than those sub-materials is also mixed into thesponge rubber.

In the extrusion body 112A, the portion where the solid rubber rawmaterial has been extruded from the solid rubber extruder 132 isprovided as the rubber base 113. The portion where the sponge rawmaterial has been extruded from the sponge extruder 134 is provided asthe cushion layer 118. The portion where the sponge raw material hasbeen extruded from the other sponge extruder 136 is provided as thehollow seal portion 124. Then, the cushion layer 118 and the hollow sealportion 124 may be linked to each other. In this case, the same spongerubber raw material may be extruded for the cushion layer 118 and thehollow seal portion 124 so that the number of the sponge rubberextruders can be reduced to one. For the insert core member 116A, asheet material composed of stainless steel or steel may be used.

Next, a vulcanization step is carried out. In the vulcanization step,the extrusion body 112A of unvulcanized rubber is passed through amicrowave heater (UHF) 144 and a hot-air vulcanizer (HAV) 146 so thatthe rubber is vulcanized. This step is carried out at a temperature in arange of from 180° C. to 240° C. suitable for vulcanizing EPDM.Incidentally, the vulcanization time (the time to pass through theheater and the vulcanizer) is about in a range of from 3 min to 10 min.The vulcanized extrusion body 112A is passed through a cooling unit 148so as to be cooled down to about 100° C. Then, in this vulcanizationstep, the foaming agent in the EPDM sponge rubber expands so thatpredetermined sponge rubber can be obtained. The above process issubstantially same as the process for preparing the weather strip body113 as aforementioned.

Succeedingly, a step for laminating the skin layer 120 is carried out.That is, in this step, a material in which a foaming agent has beenadded to thermoplastic elastomer is extruded from an extruder 150 so asto form a skin sheet 120A. At the same time, a bonding sheet 122Acomposed of PE is extruded from one extrusion head toward the backsurface side of the skin sheet 120A so as to form a lamination. As thethermoplastic elastomer, a composition of 80 parts by weight of EPDM and20 parts by weight of polypropylene (PP) may be used. Incidentally, thethermoplastic elastomer is heated to be in a range of from 200° C. to260° C. in a cylinder of the extruder 150, so that the thermoplasticelastomer is melted. At this time, the dispersed foaming agent is alsomelted to start foaming. However, the foam has not reach a cellularstate due to the pressure in the cylinder. As soon as the thermoplasticelastomer is extruded from the extrusion head and exposed to theatmospheric pressure, the foam expands to form cells. Thus, the foamedskin sheet 120A is formed.

The lamination sheet of the skin sheet 120A and the bonding sheet 122Ais guided to pressure rollers 152. The lamination sheet is pressed ontothe extrusion body 112A by the pressure rollers 152. At this time, thetemperature of the skin sheet 120A drops down before it reaches thepressure rollers 152. When the skin sheet 120A reaches the pressurerollers 152, the temperature of the skin sheet 120A is in a range offrom 120° C. to 140° C., that is lower than the temperature with whichthe thermoplastic elastomer is thermally deformed. That is, thetemperature is so low that the cells are not collapsed. Accordingly,even if the skin sheet 120A is pressed by the pressure rollers 152, thecells are not collapsed, but they recover and keep their foaming state.On the other hand, the bonding layer 122 is formed of PE the meltingpoint of which is in a range of from 110° C. to 140° C. Therefore, evenwhen the bonding layer 122 is guided to the pressure rollers 152, thebonding layer 122 is softened sufficiently so that it can be thermallybonded to the cushion layer 118 easily. Thus, the lamination sheet canbe thermally bonded with the cushion layer 118 without increasing thesurface temperature of the skin layer 120 and without collapsing thecells of the foam. Through the bonding step with the pressure rollers152, the skin layer 120 is bonded with the cushion layer 118 through thebonding sheet 122A by thermal bonding.

Succeedingly, the vulcanized extrusion body 112A with the skin layer 120bonded thereto is cooled by a not-shown cooler. Further, the extrusionbody 112A with the skin layer 120 is bent into a U-shape in section by aprocessing machine. After a step of cutting the extrusion body 112A intopredetermined length, or the like, the weather strip 100 in FIG. 6 iscompleted.

As has been described above, according to the weather strip 100 in thisembodiment, because the skin layer 120 is a foamed layer, a soft feelingon the external appearance can be provided in the region where theweather strip 100 is exposed in the cabin of the vehicle. In addition,the cushion layer 118 is provided in the substantially whole regionunder the skin layer 120. The cushion layer 118 can provide a softfeeling on the sense of touch. Thus, the weather strip 100 can provide asoft feeling not only on the external appearance but also on the senseof touch.

In addition, all of the attachment base portion 112, the cushion layer118, the bonding layer 122, and the skin layer 120 are formed ofmaterials of olefin series, so that they are thermally bonded with oneanother firmly, and there is no fear that they peel off. In addition,the bonding layer 122 is formed of PE the melting point of which is low.Thus, even if the temperature of the bonding layer 122 is lowered totemperature with which cells of foam of the skin layer 120 are notcollapsed when the skin layer 120 is pressed by the rollers, the PE canbe thermally bonded with the cushion layer 118 firmly. Further, becauseall are formed of materials of olefin series, it is not necessary to usea special two-layer bonding film described in the background art. Thus,the manufacturing cost can be reduced.

Further, the skin layer 120 can be changed easily in accordance with thecolor tone of the interior member W inside the cabin of the vehicle. Itis therefore easy to make the skin layer 120 match to the color tone ofthe cabin of the vehicle.

In addition, according to the weather strip 100, the processing ofbonding the cushion layer 118 and the skin layer 120 is carried out on acontinuous production line after the extrusion body 112A has beenextruded. Thus, the weather strip 100 is superior in productivity.

Incidentally, the present invention is not limited to theabove-mentioned embodiment. For example, the weather strip may bemodified as follows.

FIG. 9 is a sectional view illustrating a weather strip 100 showinganother embodiment. In the weather strip 100, an outer layer portion 118b which is a part of a sectionally U-shaped attachment base portion 112outside the insert core 116 is formed of sponge rubber. This outer layerportion 118 b belongs to a cushion layer 118. In this case, when ahollow seal portion 124 and an outside lip 118 a are also continuouslymolded integrally, the weather strip 100 can be manufactured by onesponge rubber extruder. In addition, the thickness of sponge rubber canbe made larger than that in FIG. 6. Thus, a softer feeling can beobtained.

The skin layer 120 was bonded with the extrusion body 112A by thepressure rollers 152 in the process of manufacturing the weatherstrip100. However, the present invention is not limited to such a process.The skin layer 120 may be bonded by a bonding agent or the like inanother process. In the forgoing, several embodiments have beenindividually described, however, these embodiments can be combined tothe possible extent.

Further, the present invention is not limited to the above-mentionedembodiment. It can be carried out in various modes without departingfrom the scope of the invention.

1-12. (canceled)
 13. A method for manufacturing an automobile weatherstrip, comprising steps of: extruding ethylene-propylene rubber to forman extrusion body as an attachment base portion and a cushion layer;vulcanizing said extrusion body; extruding a skin sheet of foamableolefin thermoplastic elastomer to form a skin layer; extruding a bondingsheet of an olefin material for forming a bonding layer to be interposedbetween said skin layer and said cushion layer; laminating said skinsheet, said bonding sheet and said extrusion body, respectively at thepredetermined temperatures, to thereby keep cells of foam of said skinsheet; and laminating and pressing said skin sheet, said bonding sheetand said extrusion body to thereby thermally bond said skin sheet ontosaid cushion layer through said bonding sheet.
 14. A method formanufacturing an automobile weather strip, comprising the steps of:extruding a rubber to form an extrusion body; vulcanizing said extrusionbody; extruding a skin sheet of foamable thermoplastic elastomer;laminating said skin sheet and said extrusion body, respectively atpredetermined temperatures to thereby maintain foam cells of said skinsheet; and pressing said skin sheet and said extrusion body to therebythermally bond said skin sheet onto said extrusion body.
 15. A methodfor manufacturing an automobile weather strip, comprising; extruding arubber to form an extrusion body; vulcanizing said extrusion body;extruding a skin sheet of foamable thermoplastic elastomer; extruding abonding sheet of an olefin material to be interposed between said skinsheet and said extrusion body; laminating said skin sheet, said bondingsheet and said extrusion body, respectively at predeterminedtemperatures to thereby maintain foam cells of said skin sheet; andpressing said skin sheet, said bonding sheet and said extrusion body tothereby thermally bond said skin sheet onto said extrusion body throughsaid bonding sheet.
 16. A method for manufacturing an automobile weatherstrip according to claim 15, wherein said extrusion body includes anattachment base portion and a cushion layer, and said skin sheet isbonded onto said cushion layer through said bonding sheet.
 17. A methodfor manufacturing an automobile weather strip according to claim 15,wherein said rubber includes an EPDM rubber, said foamable olefinthermoplastic elastomer includes a TPO, and said olefin materialincludes LLDPE.